1. Field of the Invention
The embodiments discussed herein relate to a power module that includes switching elements connected in a half-bridge configuration and a drive circuit for driving these switching elements and that is able to implement a desired logic function or parameter in the drive circuit.
2. Background of the Related Art
Industrial motor drive devices and server power supply devices use power modules that are operated by performing on-off control of switching elements connected in a half-bridge configuration. In a power module, a high voltage integrated circuit (hereinafter, HVIC) is used as a control integrated circuit for driving switching elements connected in a half-bridge configuration. The HVIC includes a high-side circuit for controlling the high-side switching element of the half-bridge circuit and a low-side circuit for controlling the low-side switching element of the half-bridge circuit. Thereby, it is possible to drive both a high-side semiconductor element and a low-side semiconductor element by use of one integrated circuit (IC).
In such an HVIC, it is desired to implement desired logic operations or parameters in a half-bridge circuit and a low-side circuit. For example, a power module has a function of protecting it from a drop in power supply voltage, overcurrent, and overheat. With respect the function, there is a demand for changing a priority order of alarming that is made when a voltage drop, overcurrent, or overheat is detected. In addition, there is another demand for appropriately changing a threshold to be used for detecting the voltage drop, overcurrent, or overheat.
These demands are met by providing a programmable circuit in the power module and writing data for implementing a logic function or parameter data indicating a threshold into the programmable circuit. It is known that a level shift circuit is provided in such a programmable circuit in order to isolate the programmable circuit from other circuits or to convert a voltage level, with ground as a reference potential (for example, refer to Japanese National Publication of International Patent Application No. 2014-515843 (Paragraphs [0078] and [0087], and FIG. 2)). In addition, the circuit taught in Japanese National Publication of International Patent Application No. 2014-515843 uses a JTAG (Joint Test Action Group) interface for writing program data to a programmable circuit.
By the way, in a power module, a high-side programmable circuit connected to a high-side circuit is referenced to a midpoint potential of a half-bridge, and a low-side programmable circuit connected to a low-side circuit is referenced to ground. In particular, the reference potential for the high-side circuit and the high-side programmable circuit varies between zero volt (V) and the power supply voltage (for example, several hundred volts) by two switching elements complementarily being switched on and off. In contrast, the circuit taught in Japanese National Publication of International Patent Application No. 2014-515843 has one system although a power system for a write circuit is independent of a power system for a programmable circuit that communicates with the write circuit, and has a reference potential that does not vary every moment, unlike the reference potential for the high-side circuit of the power module. Therefore, it is not possible to use the write circuit configured as taught in Japanese National Publication of International Patent Application No. 2014-515843, for the high-side programmable circuit and the low-side programmable circuit. That is to say, the power module needs a write circuit for the high-side programmable circuit and a write circuit for the low-side programmable circuit separately. In addition, since the high-side reference potential may rise to a very high voltage level, the high-side write circuit and the low-side write circuit need to be provided physically separated from each other.
In the above-described power module, write circuits for writing programs and data need to be provided separately for the high-side and for the low-side. Since two write circuits are needed, write ports are needed for the two systems accordingly. As a result, the power module increases in both size and cost.